This is wrong and those involved with the TV programme making these claims have acted irresponsibly and will cause ill health if it stops people taking supplements with proven benefits.
It is junk science...badly performed research that draws unreliable conclusions, reported uncritically and as fact by the media.
Media reporting on health issues is often poor...but this is a new low.
The reports are based on 2 similar papers by the same authors - http://jama.ama-assn.org/cgi/content/abstract/297/8/842 and http://www.cochrane.org/reviews/en/ab007176.html
Its hard to know where to start in terms of the problems with this research. Here are just some of the criticisms that have been reported....
Interestlingly, we learn upon reading the full-text that the researchers specifically excluded studies that reported no deaths during a trial period or follow-up. A meta-analysis that seeks to establish effects on mortality but excludes studies with no reported deaths from the pool of data to be analyzed? Hmmm...
...the studies used are all over the place, looking at different antioxidants, at different doses, at different durations, with different lengths of follow-up, in different populations - ranging from folks who were incredibly healthy to people with different diseases, with different combinations administered in different trials.
A closer look at the studies included shows that the dosage was all over the place for vitamin A - from 2000IU per day to twenty-times the upper tolerable limit (UTL) at 200,000IU per day; and beta-carotene dose ranged from a low of 1.2mg per day to 50mg per day.
Interestingly the researchers didn't take the data even further - they didn't investigate causes of death, so no one knows if deaths were related to taking antioxidants, accidents, diagnosed disease or something else. They also did not analyze for potential outcome differences between primary prevention and secondary prevention trials - basically they didn't ask if being sick (secondary prevention trials) influenced mortality outcome differently than being healthy (primary prevention trials) while taking antioxidants.
I think the point that has to be made is that this is a ‘data dredge’. The researchers did absolutely no original work, did not see a single patient, study an actual disease process. Instead, they fed data into computers, which churned out statistics this way and that.
But with all the benefits of antioxidants already well known to the well-informed, how did the Cochrane Library arrive at such a conclusion? It's easy: The researchers considered 452 studies on these vitamins, and they threw out the 405 studies where nobody died! That left just 47 studies where subjects died from various causes (one study was conducted on terminal heart patients, for example). From this hand-picked selection of studies, these researchers concluded that antioxidants increase mortality.
Just in case the magnitude of the scientific fraud taking place here has not yet become apparent, let me repeat what happened: These scientists claimed to be studying the effects of vitamins on mortality, right? They were conducting a meta-analysis based on reviewing established studies. But instead of conducting an honest review of all the studies, they arbitrarily decided to eliminate all studies in which vitamins prevented mortality and kept people alive! They did this by "excluding all studies in which no participants died." What was left to review? Only the studies in which people died from various causes.
Brilliant, huh? This sort of bass-ackward science would earn any teenager an "F" in high school science class. But apparently it's good enough for the Cochrane Library, not to mention all the mainstream press outlets that are now repeating these silly conclusions as scientific fact.
The study has been slammed by the US-based Council for Responsible Nutrition, who said the researchers "misuse[d] meta-analysis methods to create generalized conclusions that may inappropriately confuse and alarm consumers who can benefit from supplementing with antioxidants."
Moreover, Andrew Shao, Ph.D., CRN's vice president, scientific and regulatory affairs said that the combined studies were far too diverse and different in terms of dosage, duration, study population and nutrients tested that the results of the analysis were "compromised".
Additionally, Dr. Shao noted that most of the trials included in the meta-analysis tested for secondary prevention, looking at how a nutrient works in diseased populations, instead of primary prevention studies in healthy populations.
"Combining secondary prevention and primary prevention trials and then making conclusions for the entire population is an unsound scientific approach," said Shao. "Additionally, many of the trials had limitations, including the expectation that a simple antioxidant vitamin could be expected to overturn serious illness, such as cancer or heart disease. These trials likely statistically skewed the results."
Daniel Fabricant, vice president of scientific affairs for Natural Products Association (NPA), another US-based trade association, supported this view.
"Despite the authors' contention, this analysis is assessing mortality of at-risk and diseased populations - versus a healthy population - in prevention trials. The risk of mortality must be attributed to the appropriate population studied, those with an existing health condition, which it isn't in this case. Instead, those findings are generalized to a healthy general population, which is wrong on many levels," said Fabricant.
"But what's most troubling is that people who are safely and beneficially taking vitamins might stop, which may actually put their health at greater risk."
Fabricant also stated that if a true mortality risk had been apparent in any of these clinical studies using antioxidants, the study would have been halted, but none were.
"Nearly 160 million people in North America and Europe use the attributed supplements. If antioxidants were a significant public health risk, as the authors speculate, it would have become clearly apparent by now," he said. "This is obviously not the case: the negative effect they refer to has not been seen in the population."
Read more detailed comments here:
Antioxidant Supplements Dangerous?
No comments:
Post a Comment